shell中单引号双引号反引号的区别

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1、shell中单引号，双引号，反引号的区别？
2、shell IFS解惑？

2017.4.19答
在shell中这几个引号的区别如下，注意只是shell。
反引号,反引号中的命令会被执行并返回命令执行的标准输出。
相当于$（cmd）
单引号，相当于原始字符，单引号中字符是什么就是什么
例如：echo '$PATH' 显示结果就是$PATH
双引号，双引号会解析$
例如 echo “$PATH” 会显示环境变量的值.

IFS是什么?
内部域分隔符
https://bash.cyberciti.biz/guide/$IFS
The IFS is a special shell variable.（一个特殊的shell变量）
You can change the value of IFS as per your requirments.
The Internal Field Separator (IFS) that is used for word splitting after expansion and to split lines into words with the read builtin command.
The default value is . You can print it with the following command:

cat -etv <<<”$IFS”

IFS variable is commonly used with read command, parameter expansions and command substitution.

From the bash man page:

The shell treats each character of IFS as a delimiter, and splits the results of the other expansions into words on these characters. If IFS is unset, or its value is exactly <space><tab><newline>, the default, then sequences of <space>, <tab>, and <newline> at the beginning and end of the results of the previous expansions are ignored, and any sequence of IFS characters not at the beginning or end serves to delimit words. If IFS has a value other than the default, then sequences of the whitespace characters space and tab are ignored at the beginning and end of the word, as long as the whitespace character is in the value of IFS (an IFS whitespace character). Any character in IFS that is not IFS whitespace, along with any adjacent IFS whitespace characters, delimits a field. A sequence of IFS whitespace characters is also treated as a delimiter. If the value of IFS is null, no word splitting occurs.

The default value of IFS is a space, a tab, and a newline.

 echo $IFS|od

$# shell参数个数

$* 和 $@如果没有双引号没什么区别，
如果用双引号括起来，则有区别了，
“$*”会把多个参数当成一个整体，可以理解为是以一个单字符串显示所有向脚本传递的参数。
“$@”还是会变成多个参数，相当于参数列表